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The Alien Worm

Posted by Don McLenaghen on March 15, 2012

There are a number of things that we think of a ubiquitous in the natural environment, trees, bees, birds and earthworms. There is a problem here, apparently one of those elements are unnatural…at least in Canada.  To be placed in the unbelievable things I have learned from my pod-casts we must add a new chapter. It seems that in Canada and the northern USA, there is no such thing as a natural or indigenous earthworm well, to pull back a little on the hyperbole, areas along the Pacific coast that escaped glaciation do have some indigenous worms.

It seems that all our local earthworms were wiped out by the last major ice age. Now you might say that “Don, you’re daft; I see birds munching on earthworms every rainy day. At this time the sidewalk is full of them. If the earthworm were wiped out, how do you explain these?”

Well, it seems to be another plaque we can rest at the feet of European settlers. Seems the little buggers stowed away in the ballast of ships, plants imported and on purpose by settlers who believed that earthworms were necessary for a healthy garden.

It seems that invading earthworm, which has been advancing for about three hundred years, is an urban or at least people lover. Apparently everywhere people have developed…roads, pipelines, etc…invading earthworms can be found up to a mile away.

Now, it also seems that although we think of earthworms as a positive influence for plants; after all they are famous for recycling nutrients by speeding up decay. They aerate the soil and provide a food source for lizards, mice and of course birds. This may be true in Europe where most of our worms evolved but to be beneficial in nature there must be co-evolved. The forest and animals of Europe have evolved WITH the earthworm, so there it is beneficial and symbiotic.

The arboreal forest of northern Canada has evolved a slower decay cycle based on fungus and bacteria. Here the earthworm has upset the balance affecting both plants and animals. They are evasive because they have not evolved here and do not fit into the existing biosphere…it is altering and offsetting that natural balance.

The effects of alien worms

Some may argue that if earthworms are an evasive species how come the prairies are not affected? I think thy likely were, however that damage was done over a hundred years ago and coincided with intensive agriculture…so which changed the prairies more is debatable and besides back then, who cared about the ‘natural prairies’ so long as the crops came in.

The northern and less agri-friendly regions thought were spared both the terraforming of modern farming but also the introduction (by man) of the invading earthworm. That all changed in the last half-century as northern forests have been inundated with logging roads and the inaccessible regions become accessed in the never ending search and extraction of natural resources. As roads and development spread north and into ‘wild’ areas, so goes the worms.

In a recent paper, it appears that small plants and some tree saplings are struggling under the new growth conditions. At least one species of bird is suffering because of the loss of leaf litter and aforementioned plants…their nests become easier to see and thus predation increases. The fat nightcrawler, beloved of anglers, helps adult salamanders because they’re a fat source of food but are killing off the juvenile salamanders who are unable to eat the night crawlers that replaced the indigenous species.


ATTACK OF THE ALIEN WORM…coming to a theatre and forest near you!

2 Responses to “The Alien Worm”

  1. rkbooth said

    Interesting post. Would you mind if I linked to some of the images you have here from my blog? Or is there a source for the images AW1, AW2, and AW3 that I could track down myself? Thanks, Bob.

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